In co-pending U.S. Ser. No. 07/402,179 filed Sept. 1, 1989, now abandoned there are disclosed pyridazinones useful in treating persons diagnosed as having congestive heart failure of the following formula (I): ##STR2## wherein: R.sup.1 is H or lower alkyl;
R.sup.2 is H, halogen, CF.sub.3, CN, lower alkyl or lower alkoxy; PA1 L is an amide-containing alkylene chain or an alkylene chain and: PA1 R.sup.3 and R.sup.4 represent a variety of substituents.
A method of making compounds of formula (I) involves reaction of a phenol of the following formula (B): ##STR3## wherein R.sup.1 and R.sup.2 are as defined for formula (I) and the wavy line at the 5-position of the pyridazinone ring indicates that the bond could be up or down or a mixture of the two such enantiomers. An object of the present invention is to provide a method of obtaining the compound formula (B) enriched in one or the other of such enantiomers.
Publications relevant to the art of kinetic resolution include P. Kalaritis et al in J. Org. Chem., 1990, 55, pp 812-815, George M. Whitesides in Angewandte Chemie Vol. 24, No. 8, August 1985, pp 617-638 and European Patents 325,954 and 325,971 to John J. Partridge et al.